Grades 3–5 · Everyday Life
How does rice become softer as it cooks?
A dry rice grain is firm, but cooking it with water can make it soft and swollen. Inside the grain are many tiny packages of starch, called starch granules. Their size and arrangement are too small to see by looking at a whole grain.
In the diagramHeat and water change starch inside riceUncooked grainGrain taking in waterWater entersHeat transferredStarch granulesGranules swellTheir ordered inner structure loosens.This change helps make the grain softer.Starch granules are enlarged and schematic.
As the grain heats and takes in water, the starch granules change. Water enters them, they swell, and their ordered inner structure loosens. This change is called gelatinization. It helps explain why cooked rice has a different texture from dry rice. Heat and water work together in this process.
The water entering a grain comes from its surroundings. As water moves inward and the starch changes, the texture of the whole grain changes too. Real rice varieties do not all cook alike. Their starch differs, and the available water also affects texture. Heat and absorbed water help explain the change from a firm grain to softer cooked rice.
About this explanation
Starting knowledge: Recognize a rice grain and understand that water can enter a material.
Sources
- USDA Agricultural Research Service — Gelatinization and pasting properties of rice starch modified with 2-octen-1-ylsuccinic anhydride
- Kagawa University researchers; National Library of Medicine — The relationship between translucency of rice grain and gelatinization of starch in the grain during cooking
- USDA Agricultural Research Service — Influence of Water to Rice Ratio on Cooked Rice Flavor and Texture